W124 1991 - third fan clutch appears to be failing - I have even tried the 603 conversion... I am really really wanting to convert to electromagnetic... I found a reference to early 190E that has electro magnet driven fan... has enyone contemplated this type of remedy? alternately has anyone found the viscous coupler brand that really lasts... so far I have tried Behr / ACM / Hamburg Technic.

I have an OM606 engine and its using a MB star OM603 part which was dead and I refilled myself, its working perfect. It engages when the airflow gets hot. If your radiator or condenser is plugged with dirt, bugs, road oil etc, the cooling air wont flow through them and the clutch will almost never work.

The clutch will only work when the air contacting its face is real toasty i.e. A/C running in warm weather and driving slowly. A basic operational test is to test it first thing in the morning, it should be coupled and the fan should roar for about 5 to 15 seconds then slow down.

Rather than a 201 fan, try a Spal or OE quality electric fan. Get the biggest one you can fit ahead of the water pump. You'll need more than the basic specs because you can fit a deeper motor as long as it's offset from the water pump flange which isn't centered against the radiator anyway.

If you have a genuine clutch with you you can test the initial spin up a cold then fill some silicone oil in it to make it work again. The original part for your engine should be the OM603 clutch with the large blade fan.

Rather than a 201 fan, try a Spal or OE quality electric fan. Get the biggest one you can fit ahead of the water pump. You'll need more than the basic specs because you can fit a deeper motor as long as it's offset from the water pump flange which isn't centered against the radiator anyway.

Just from it's brand name Hamburg Technic sounds like junk.

Sixto
87 300D

Sorry - maybe it is the 606 rather than the 603 ( my MB model numbering knowledge is well.. basic at best ) - was referencing based on faulty memory - it is a viscous clutch numbered 606 200 01 22 ( ACM Brand ) and a fan numbered W0133-1717663 ( OES Genuine - Fan ) it was based on a old thread I found but not sure where it is anymore.. found the receipts from the purchase in 2010.

Ok so do you think a electo magnetic conversion is an undoable option... Alittle loath to do the electric fan conversion as it places a heavy electric load ( of coarse many cars use them and work fine ) - just my attempt to keep things roughly setup as OE.. .

If you have a genuine clutch with you you can test the initial spin up a cold then fill some silicone oil in it to make it work again. The original part for your engine should be the OM603 clutch with the large blade fan.

Yes the Hamburg.. does sound like junk and was .. the problems experienced are these...

2009 was heating up on small hills .. did a head gasket / new radiator / new viscous coupling / backwashed the condensor fins / added thermo fan switch wired into low speed fan side to initiate at 192 F - repairs worked for some time .. a year then on large hills on highway ( central PA ) not rockies ... heating up couldnt use A/C 100 to 110 at hill top - new viscous again... now again same manifestation .. cools right off as soon as load is removed... low speed operation is fine. flat and moderate hills are fine although temp responds to load more than I like which is why I did the Head gasket in 09... I have good power output / no trans slippage / the only other thing to add and I dont know if it is realted is the hydraulic line to the power steering pump pulses every five seconds and the ASD resoevior fluid is pretty hot after driving .. to such an extent that the Left hand fender top/edge at hood line is hot to the touch.. I dont see how that would relate but it is a feature

How big a fan can you hang on a 201 electro-clutch? IIRC 201 fans are little 5-bladers that would look small in a Civic.

Anyone remember those 70s Datsun FWDs with a little fan to keep the carburetor from vapor locking?

Sixto
87 300D

reservoir pressure cap is 3 years old,

the thermostat I changed in 09 with the work i did but it had a slightly higher opening temp ( not OE but rated at the same temp ) then the original and so I changed back to the Oe that was in it. I need to order a few things from the dealer so I will get a new OE one .. hope that helps.. rightly or wrongly I tend to think problems are caused by large problems and it is good to be reminded of the simple things...of course winter is coming so I should be good for a few months come october but it is unnerving to have this issue keep reocurring .. feels as though I am not getting to the bottom of it.
by the by I wonder if anyone has ever experimented removing the electric fan shroud ( leaving the fans in place ) to allow greater air flow.. that shroud always reminds me of the big covers the big trucks use in the winter time.. I dont know why they would block so much of the natural air flow.. but then I wasnt invited to the design meetings - plus I dont speak German .. and I am sure that there is a good reason.

I have an OM606 engine and its using a MB star OM603 part which was dead and I refilled myself, its working perfect. It engages when the airflow gets hot. If your radiator or condenser is plugged with dirt, bugs, road oil etc, the cooling air wont flow through them and the clutch will almost never work.

The clutch will only work when the air contacting its face is real toasty i.e. A/C running in warm weather and driving slowly. A basic operational test is to test it first thing in the morning, it should be coupled and the fan should roar for about 5 to 15 seconds then slow down.

What problems are you facing?

The first thing in the morning test...

I am not clear is this at idle that you will experience a roar for the 5 to 15 seconds ? I will check it in the morning but I am pretty sure it does not do that. If I can ask a series number question what is a OM603 vs OM606? ... maybe it was a OM603 clutch that I am using. ( what years and model number is the OM603 - I can do a part look-up and cross check )

Define normal. 3 of my 4 603s did. I really pushed the '87 SDL up the Tejon pass southbound (3000' over 4.5 miles) once and it got to about 110*F. Keeping up with fast lane traffic they rarely hit 100*F.

The 603 engine is found in the '87 300D/TD, 86-87 300SDL, 90-91 350SD/SDL, 92-95 300SD/S350. The 606 engine is found in the 95-99 E300.

Saying a 603 engine has a 606 clutch is subject to interpretation. It could mean that the clutch is what's specified for some variant of the 606 and not for the 603, or the 603 part number was superseded by a 606 part number. The clutch from the turbo 606 was all the rage a few years ago because it was an easy fit in any 603 application at about half the cost of the specified 603 clutch part number. Don't take this to mean that the 606 clutch performs better in the 603. Folks usually wait too long to replace the clutch so any clutch would be an improvement.

I am not clear is this at idle that you will experience a roar for the 5 to 15 seconds ? I will check it in the morning but I am pretty sure it does not do that. If I can ask a series number question what is a OM603 vs OM606? ... maybe it was a OM603 clutch that I am using. ( what years and model number is the OM603 - I can do a part look-up and cross check )

The roar test cannot be heard at idle speed, best is to start open the hood and start the engine, immediately verify the airflow from the fan and move the pump linkage from the engine room, the fan should blow a gust of air and sound loud also, hold it at 2000 rpm and you will feel, see and hear it idle down and decouple from the engine rpm, that means that the clutch has its fluid in it, its not completely bad.

You could also try a citric acid flush and thoroughly clean out the expansion tank too, if any sort of stop leak was added it will plug up the little holes in the tank that make the coolant move around, if coolant cannot move at the required rate the system will cavitate.

The 603 engine is found in the '87 300D/TD, 86-87 300SDL, 90-91 350SD/SDL, 92-95 300SD/S350. The 606 engine is found in the 95-99 E300.

Saying a 603 engine has a 606 clutch is subject to interpretation. It could mean that the clutch is what's specified for some variant of the 606 and not for the 603, or the 603 part number was superseded by a 606 part number. The clutch from the turbo 606 was all the rage a few years ago because it was an easy fit in any 603 application at about half the cost of the specified 603 clutch part number. Don't take this to mean that the 606 clutch performs better in the 603. Folks usually wait too long to replace the clutch so any clutch would be an improvement.

Sixto
87 300D

Sixto thanks...

to clarify... the 606/603 clutch mod was based on an old thread which I now found 2010 in which as you say the 603 owners were discussing the use of the 606 clutch... in my case I used the 606 clutch and fan for my W124 which seemed to work well albeit mounted back towards the water pump 3/8" to 1/2" more than stock. At this point I am considering ( after a new thermostat) going back to stock using the clutch offered here on fastlane... wish I could mod to a electromagnetic but probably not worth the time it would take to find parts and fabricate.. bottom line the system is designed to work and did work for a long time and unless I have a renewed head gasket or head problem ( really hope not - it was a big job ) the system should be able to be returned to a proper working state.